Loading/unloading terminal, especially for loading or unloading of petroleum products

ABSTRACT

A loading/unloading terminal, especially for use in loading or unloading of petroleum products comprises a barge (1) provided with a downwardly open receiving space (2) for reception and releasable securement of a submerged buoy (20), and a submerged buoy (20) of the type comprising a bottom-anchored center member (21) for passage of medium from or to a transfer line (32) attached to the center member, and an outer member (23) rotatably mounted on the center member (21) to allow turning of the barge (1;40) about the center member (21) when the outer member (23) is secured in the receiving space (2) of the barge. The barge (1) further is provided with a coupling means (4) for connection of the passage (22) of the center member (21) to a line (9) for medium transfer to or from an adjacent conventional tanker, and with a means (10-14) for hoisting and introduction of the buoy (20) into the receiving space.

BACKGROUND OF THE INVENTION

This invention relates to a loading/unloading terminal, especially foruse in loading or unloading of petroleum products.

In connection with offshore loading or unloading of hydrocarbons (oiland gas) there has been developed--during the recent years--a specialtechnology called STL technology, wherein the abbreviation STL standsfor "submerged turret loading". This technique is based on the use of aspecial buoy construction consisting of a submerged buoy which comprisesa bottom-anchored centre member having a passage for transfer of aflowable medium from or to a transfer line attached to the centremember, and an outer member which is rotatably mounted on the centremember and is arranged for introduction and releasable securement in asubmerged downwardly open receiving space at the bottom of a vessel. Theouter member of the buoy constitutes a buoyancy member, and when thebuoy is not in use it floats submerged at a chosen distance below thesea level, the buoyancy of the buoy corresponding to the weight of theanchoring system of the buoy. In use, the buoy is hoisted up by means ofa pick-up line attached to the buoy, and the outer member of the buoy issecured in the receiving space in the topical tanker, for instance aso-called shuttle tanker. The buoy structure allows the vessel duringloading/unloading operations to turn about the bottom-anchored centremember of the buoy, under the influence of wind, waves and watercurrents. Thus, the buoy constitutes a submerged rotating body("submerged turret"), which has resulted in the above-mentioneddesignation of the utilized technique.

The STL technique has turned out to have very substantial advantages inpractice, both connection and disconnection between vessel and buoybeing able to be carried out in a simple and quick manner, even in badweather with relatively high waves. Further, the buoy may remainconnected to the vessel in all weathers, a quick disconnection beingable to be carried out if a weather limitation should be exceeded.

As will be appreciated, the use of the STL technique hitherto has beendependent on specially constructed tankers, the STL buoy presupposing avessel which is provided with a submerged receiving space and thenecessary installations for hoisting and introduction of the buoy intothe receiving space, for releasable securement of the buoy and forconnection of the central passage of the buoy to a pipe system which isarranged on the vessel and communicates with the storage tanks thereof.

It would, however, be desirable to be able to use the STL technique alsoin connection with tankers which do not have the necessary equipment orare built for the STL buoy, as this will give practical as well aseconomical advantages, especially with use in smooth and relativelyshallow waters.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide aloading/unloading terminal which is suitable for the above-mentioneduse.

For the achievement of the above-mentioned object there is provided aloading/unloading terminal of the introductorily stated type which,according to the invention, is characterized in that it comprises abarge provided with a downwardly open receiving space for reception andreleasable securement of a submerged buoy, and a submerged buoy of thetype comprising a bottom-anchored centre member having a passage fortransfer of a flowable medium from or to a transfer line attached to thecentre member, and an outer member rotatably mounted on the centremember to allow turning of the barge about the centre member when theouter member is secured in the receiving space of the barge, the bargefurther being provided with a coupling means for connection of thepassage of the centre member to a line for medium transfer to or from anadjacent vessel, and with a means for hoisting and introduction of thebuoy into the receiving space.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described below in connection withexemplary embodiments with reference to the drawings, wherein

FIG. 1 shows a schematic sectioned side view of a first embodiment of abarge in a loading/unloading terminal according to the invention;

FIG. 2 shows a somewhat incomplete plan view of the embodiment in FIG.1;

FIG. 3 shows a partly sectioned side view of a STL buoy which isprovided with a bottom support means for resting on the sea bed when itis not in use;

FIG. 4 shows a side view of a loading/unloading terminal according tothe invention, having a buoy according to FIG. 3 introduced into thereceiving space of the barge, and wherein the barge is coupled to avessel at a distance therefrom;

FIG. 5 shows a view corresponding to that of FIG. 4, but of anotherembodiment of the barge designed for direct connection to a vessel, inabutment against the bow portion thereof; and

FIG. 6 shows a plan view of the embodiment in FIG. 5.

DETAILED DESCRIPTION OF THE PREFERREDE EMBODIMENTS

The barge shown in FIGS. 1 and 2, which forms part of aloading/unloading terminal according to the invention, is provided witha downwardly open receiving space 2 extending through the whole bargehull, up to the deck 3 of the barge. The receiving space is upwardlytapering and adapted for reception of a correspondingly shaped buoywhich is of the introductorily stated STL type and which may beconstructed such as further described in connection with FIG. 3.

At the deck 3 of the barge there is arranged a coupling unit 4 forconnection of the passage through the centre member of the buoy to aline for transfer of medium to or from a conventional tanker, as shownin FIGS. 4 and 5. This unit comprises a curved coupling tube 5 (aso-called "gooseneck") which, by means of a hydraulic cylinder 6, ispivotable between a stowed position and a connecting position (bothpositions shown in FIG. 1). The free end of the tube is provided with acoupling head 7 for connection to the upper end of the centre member ofthe buoy when the buoy is in place in the receiving space. The couplingtube communicates with a conduit (not shown) which is arranged withinthe barge hull and is connected to a coupling flange 8 for connection ofa hose 9 for medium transfer to/from the topical vessel.

On the barge deck there is further provided a guide frame 10 havingguide rollers 11, 12 for guiding of a line 13 for hoisting andintroduction of the topical buoy into the receiving space 2. The line isoperated by a winch means 14. Instead of a winch it is also conceivableto use a suitable jack means. On the deck there is further provided alocking means 15 for releasable securement of the topical buoy in thereceiving space. In the illustrated embodiment, this means consists ofrotatable locking elements 16 which are arranged to grip under a lockingcollar on the buoy, and which are operated by means of a suitablehydraulic drive means 17. A hydraulic power supply unit 18 for operationof the hydraulic units on the barge is suggested to be arranged belowthe deck of the barge.

The above-mentioned equipment is of a known design, and for furtherdescription of such equipment on a STL ship reference may be made toNorwegian laying-open print No. 175 420.

The buoy shown in FIGS. 3-5 is especially constructed for use in shallowwaters, and the buoy is provided with a bottom support means to beplaced at the sea bed when it is not in use. Such a buoy structure isthe subject of the simultaneously filed patent application No. 944211,and reference is here made to this application for a further descriptionof the buoy construction. Reference is also made to U.S. Pat. No.5,509,838 wherein a STL buoy of the topical type is further shown anddescribed, and to U.S. Pat. No. 5,529,521 showing different embodimentsof locking means which may also be used on the barge 1. Instead of suchrotatable locking means it is also conceivable to use horizontallymovable locking means, for example segment wedges.

The buoy 20 shown in FIG. 3 comprises a central member or centre member21 in the form of a hollow shaft having a passage 22 for the flowablemedium which is to be transferred via the buoy, and an outer member 23which is rotatably mounted on the centre member 21 and arranged to besecured in the receiving space 2 of the barge. The centre member 21 atits upper end is provided with a swivel unit 24 and a valve unit 25 forconnection to the coupling head 7 on the above-mentioned coupling unit4. The outer member 23 has a cone shape which is adapted to thereceiving space 2, and the upper part as shown has a locking collar 26for engagement with the locking elements 16 in the locking means 15arranged on the barge.

As shown, the bottom support structure 27 of the buoy consists of aring-shaped or annular support body 28 which, through a number of braces29, is attached to a reinforced holding portion 30 of the centre member21 of the buoy. The lower end of the passage 22 of the centre member isconnected through a 90° bend 31 to a transfer line in the form of aflexible riser 32 which is shown to extend horizontally outwards fromthe buoy structure.

The buoy is anchored to the sea bed 33 by means of a number (e.g. eight)of mooring lines 34 which are connected to the centre member 21 of thebuoy through respective coupling links 35 which suitably may beuniversal joints, as appears from FIG. 3. The mooring lines 34 arerelatively long, to utilize the elasticity of the lines when the buoy ishoisted up and introduced into the receiving space of the barge, asfurther described in the above-mentioned simultaneously filed patentapplication.

FIG. 4 shows an embodiment wherein the barge 1 is coupled to aconventional tanker 36 which is located at a distance from the barge.The barge is moored to the vessel by means of a mooring hawser 37, and aloading hose 38--corresponding to the loading hose 9 in FIG. 1--extendsbetween the barge and the midship manifold 39 of the vessel. As shown, apart of the loading hose may float in the sea.

FIGS. 5 and 6 show another embodiment wherein the barge 40 is designedfor direct connection to the tanker 36, in abutment against the bowportion thereof, so that the vessel and barge form a unit. The endportion of the barge remote from the receiving space here is formed witha recess 41 which is essentially complementary to the shape of the bowportion of the vessel 36. The barge can be pulled up to the vessel bymeans of the vessel's own winches (not shown), suitable fastening pointsfor the winch lines being provided on the barge. In the illustrated casethe barge is shown to be kept in position in contact with the bow of thevessel by means of a pair of lines 42 and 43. A loading hose 44 extendsbetween the barge and the vessel and is also here coupled to the midshipmanifold 39 of the vessel.

In the recess 41 of the barge there are advantageously mounted fendermeans (not shown) for abutment against the bow portion of the vessel.Advantageously, these may consist of inflatable rubber fenders. It isalso conceivable to use fenders mounted on e.g. hydraulic arms, foradaptation to different hull or bow shapes.

By means of the illustrated embodiments the STL technology may be usedin connection with conventional tankers. In relation to the embodimentin FIG. 4, the embodiment according to FIG. 5 among other things has theadvantage that one avoids the possible use of a tugboat to prevent thebarge from moving towards and impacting with the tanker.

The invention has been shown and described above in connection with abuoy which is placed at the sea bed when it is not in use. It will beclear, however, that the loading/unloading terminal according to theinvention may also be used in loading and unloading at larger waterdepths, i.e. in connection with a STL buoy of the type floating in asubmerged condition when it is not in use.

I claim:
 1. A loading/unloading terminal for loading or unloading petroleum products between a tanker and a submerged buoy, said terminal comprising:a) a barge (1; 40) provided with a downwardly open receiving space (2) for the reception and releasable securement of a submerged buoy, b) a submerged buoy (20) comprising a bottom-anchored centre member (21) having a passage (22) for the transfer of petroleum products from or to a transfer line (32) attached to the centre member, and an outer member (23) rotatably mounted on the centre member to allow turning of the barge about the centre member when the outer member is secured in the receiving space of the barge, c) coupling means (4) provided on the barge for connecting the passage of the centre member of the buoy to a line (9: 38; 44) for transferring petroleum products to or from an adjacent tanker (36) connected to the barge, and d) means (10-14) provided on the barge for hoisting and introducing the buoy into the receiving space.
 2. A loading/unloading terminal according to claim 1, provided with a mooring hawser (37) and a loading hose (38) for, respectively, mooring of and petroleum products transfer to/from a tanker located at a distance from the barge.
 3. A loading/unloading terminal according to claim 1, wherein the barge has a hull portion formed with a recess (41) having a shape complementary to the shape of the bow portion of the tanker, means (42, 43) being provided for interconnecting the barge and the tanker as a unit.
 4. A loading/unloading terminal according to claim 3, comprising fender means provided in said recess for abutment against the bow portion of the tanker.
 5. A loading/unloading terminal according to claim 4, wherein the fender means are inflatable rubber fenders.
 6. A loading/unloading terminal according to claim 1, wherein the receiving space extends through the hull of the barge, and both the coupling means and the hoisting means are arranged on the deck of the barge.
 7. A loading/unloading terminal according to claim 1, wherein the buoy has a bottom support structure (27) connected to the centre member of the buoy for supporting the buoy on the sea bed (33) when it is not in use. 